The effects of oxidation in nucleate pool boiling were investigated. Water and a refrigerant (R-ll) were boiled on commercially clean, and oxidized copper tubes. It was observed that oxidation increases the nucleate pool boiling heat transfer coefficient for both fluids. The boiling heat transfer coefficient increases with increase in the level of oxidation. A microphotograph examination of the oxidized surface shows that oxidation tends to make the surfaces rougher and increased cavity sites and active nucleation sites were clearly observed during boiling. The contact angle of water on copper with different levels of oxidation was also measured. The contact angle was found to decrease with increase in the level of oxidization.